I’d say because birds are free and independent. The feminist movement is all about being your own person any not having to defend on a man. Women can make their own decisions for themselves. This is why the bird reinforces a feminist theme.
The setting builds atmosphere to whether the environment in the story is pleasant or disturbing, it can build a sense of uneasiness if the author describes darkness and destruction in the story . Likewise , if a setting is full of light and flowers , it implies a happy and pleasant mood.
I'm not entirely sure but I think it would be A because usually a character that is not the main voice but more of a sidekick is meant to keep the main character's quest or mission from getting too boring. Logically he/she would be meant to be a funny character to lighten up the mood of the book.
To set off a parenthetical expression I believe.
Tell an adult. If it's at school talk to a teacher or principal. Bullying is not acceptable.